PDP, Reflecting on my Technical Research Report

Over the course of two summer placements I was able to gather a lot of research about press form manufacturing, working for a company called Gestamp. This led me to the conclusion that writing about this process would allow for plenty of research to be undertaken to fully understand what this process holds and how it stands in industry today.  The focus on sustainability was a key factor, as I am fully aware of the increase in the need for recycling and how big companies ensure that their processes are sustainable, both environmentally and economically.

My time in industry showed me that press forming is still a widely used practice and that there are many applications that use press forming to create both small scale and large scale products. As the company uses their machinery to press form car body parts, I was able to learn that the majority of the materials used in the process are used to create the parts with only 30% of the raw materials were wasted. This waste however, adds to the economic sustainability of the process as its then sold onto scrap merchants who recycle the waste and the money from this is then given back to original producer of the raw material to allow for purchasing and manufacturing of new materials.

B vs P

Figure 1 (Blanking Vs Punching)

When initially writing my technical report, focusing on the technology was vital to get across exactly how press forming works, including the different processes presses go through to produce a variety products. This included the basic operation presses perform through punching and blanking and the different types of press, including Hydraulic, Mechanical and Servo that all use different types of driving motion to form the metal sheets into the desired shape. Punching and blanking shown in figure 1 and the types of presses shown in figures 2 respectively.

Figure 2 (Gupta and Prateek, n.d.) (Tyagi, 2012) (Aida-global.com, 2008)

As further research showed just focusing on the technology was not appropriate as the materials used in this process were vital to understand exactly how the process works and why it is still viable in today industries.

From this, time was spent understanding the different types of metal that were used in mass producing parts from press forming. It was clear to me that steel and aluminum were the main materials used in press forming, this is shown by the research undertaken, showing how these types of metals can produce high strength products with low weights, that when certain forces applied to the sheet metal can be deformed into a variety of desire shapes. The basics of which can be shown in figure 3 below, showing how metals are deformed due to the amount of strain applied.

Figure 3 (Suradi, 2017) (a) (Necking Diagram) (b)

The process of writing my technical report has so far taught me about correct writing skills, being able to interpret the information I was gathering from books, articles and research documents I was reading.

It was from this point that I started to consider the sustainable aspects of other manufacturing processes and how the use of press forming, which is a sustainable process, can replace other un-sustainable processes. I quickly realised that producing anything from plastic can create a non-recyclable product and even with today’s technology, we are still not recycling enough waste as we could. This led me to finding the need for a new design, simply design out plastics.

This idea of designing out plastics is something that I will be considering for future design project. It was intriguing to see how much man-kind wastes and the problems this causes. If all it takes is to consider different materials and the way we use products, it is a shame that we don’t do more as society to provide the most sustainable future we can.

After understanding that a massive 42% of all ‘bulky waste’ was furniture (Thersa.org, 2015), it was clear to me that, even with the amount of chairs out there that could replace plastic, there is still not a design that can be quickly manufactured, completely recycled, and easy to produce in large quantities, replacing the need for the mass production of plastic chairs.

concepts

Figure 4 (Concept Design)

For me, this project became increasingly interesting as it moved from the technology of press forming, to the understanding of a new design, to the design itself. At this point, when coming up with the concepts for the design, I was able to use the research and knowledge I had gained to understand what features the design would need and how it would be manufactured. Shown in figure 4.

The final design (figure 5) came about as a combination of: the evaluation of each concept, further research into the comfort and stack-ability of a chair and the addition of a feature to both strengthen and reduce the weight of the overall design.

Final Chair collageFigure 5 (Final Chair Concept)

As shown here I was able to develop and come up with a new design for a press formed chair. This has taught me how to correctly design for press form manufacturing, including the features than can be added to the design, and the overall form that can be achieved. I believe that with more development the aesthetic and the weight of the chair can be improved for better use.

Throughout this project, research was done to find the relevant information using all manner of documentation including: books, articles, web references, imagery and primary sources. This enabled me to put together a coherent report about the process of press forming and the sustainable aspect is involves.

Upon reflection, I have enjoyed learning about the process of press forming and how it still plays a significant role in today’s society. The implications of having such a sustainable process has allowed me to appreciate to different style of manufacturing and how every day plastic objects can and should be turned into re-usable, renewable products that have a minimal effect on the environment. Being able to design a new product around press forming was a significant process to help me further my knowledge on the subject and produce a new design that would suit a wide variety of people. If I were to re-visit this, I would aim to undergo more research into the process of renewable energies, giving more focus on the other manufacturing processes that are fully sustainable.

This project has given me an insight into my future, from this I am considering a career in the manufacturing industry helping to develop new techniques to reduce waste and lower the environmental impact that the industry is still accountable for. It seems that the manufacturing industry primarily prioritises profit; I would like to change, through design, the industry, to better focus on sustainable practice in broadest sense. Not only working towards environmental sustainability but also ensuring the sustainment of a company and the industry. This will be done by critiquing the process that all products go through thus attempting to reduce waste, increase re-usability, and encourage recycling.

Bibliography:

Thersa.org. (2015). Report: The Great Recovery – Rearranging the Furniture – RSA. [online] Available at: https://www.thersa.org/discover/publications-and-articles/reports/the-great-recovery-rearranging-the-furniture [Accessed 7 Dec. 2017].

Images:

[Figure 1] Blanking Vs Punching, Image Authors own.

[Figure 2] Gupta and Prateek (n.d). NC Hydraulic Press Brakes | Micro Hydro Technic. [online] Microhydrotechnic.net. Available at: http://www.microhydrotechnic.net/nc-hydraulic-press-brakes/ [Accessed 2 Nov. 2017].

&Tyagi, V. (2012). sheet metal working. [online] Slideshare.net. Available at: https://www.slideshare.net/vivcool1/sheet-metal [Accessed 1 Dec. 2017].

& Aida-global.com. (2008). Servo Press Technology, DSF Series, Direct Drive Servo Presses, from AIDA. [online] Available at: https://www.aida-global.com/direct-drive-servo-former/#1_1 [Accessed 1 Dec. 2017].

[Figure 3] (a) Suradi, E. (2017). Why does the stress-strain curve decrease?. [online] Engineering.stackexchange.com. Available at: https://engineering.stackexchange.com/questions/13583/why-does-the-stress-strain-curve-decrease [Accessed 4 Dec. 2017].

[Figure 3] (b) Necking Diagram, Image authors own

[Figure 4] Concept Design, Image authors own

[Figure 5] Final Chair Concept,  Image Authors own

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Post Race following on from the PDP

Overall the day was successful, even though we had a few errors when competing the course, we were still able to finish with a respectable time of 1:42 seconds, and after weighting the car at 400g, we are now able to work out the approximate speed it was doing.

As the track was 10 metres long, and the car was able to compete this in 102 seconds, this means that the average speeds of the vehicle was 10/102 = 0.1 m/s, which is very slow unfortunately. Although the weight had been reduced using lighter materials, and less components, the car was still slower than expected. I believe this was due to two problems we encountered, this first being the wheel at the front of the vehicle. The silicon glue used to attach the wheels to the holder may have caused some of the balls to have locked up since the original testing. The second area for concern were the sensors themselves, we believe that they may have been slightly to far apart when going round this particular track. In the tests on tracks we had set up, the sensors did work, this may have been because the turns on the final track were sharper than originally thought.

On the plus side the car did was able to follow the follow the line and was even able to make it around its sufficient time. It was great to see the code still working properly, to stop the car when it had reached the black finish line, which aloud us to remove the battery and egg with ease.

Overall I have enjoyed this project and the fact is has expanded my knowledge on coding, electronics and mechanical aspects has been great. I now look forward to my technical report and researching into areas of great interest for myself will help me to further understand a wide variety of different manufacturing techniques, past what I have already gained this term.

 

PDP for RTS Line Tracking Car

This is the PDP for the RTS electronic line tracking car. First things first, was to finalise the electronics and the coding that will drive the car forward. At first, we believed light sensors would be a good way to read the black line. This is the code and electronic set up we had for this operation:

pdp1

int LDR = 0;    
int LDRValue = 0;    
int light_sensitivity = 100;  
int LDR2 = 1;
int LDRValue2 = 1;
int LDR3 = 2;
int LDRValue3 = 2;
void setup()
  { Serial.begin(9600);         
    pinMode(13, OUTPUT);    
  }
void loop()
  {    LDRValue = analogRead(LDR);     Serial.println(LDRValue);      
    delay(50);       
    if (LDRValue < light_sensitivity)
      {        digitalWrite(13, HIGH);
}
    else
 {        digitalWrite(13, LOW);
    }
    LDRValue2 = analogRead(LDR2);    Serial.println(LDRValue2);      
delay(50);      
    if (LDRValue2 < light_sensitivity)
      {        digitalWrite(13, HIGH);
}
    else
      {        digitalWrite(13, LOW);
}
      {    LDRValue3 = analogRead(LDR3);  Serial.println(LDRValue3);    
delay(50);      
    if (LDRValue3 < light_sensitivity)
      { digitalWrite(13, HIGH);
  }
    else
      {        digitalWrite(13, LOW);
} } }

This was met with troubling results as there was no real value that could we could define that would allow for either on or off. This is because of the Analog nature of the light sensors that can give you an infinite number of values. It was here we decided it was best to get IR sensors that work on a digital scale, so either on or off.

But before we move onto the next sensor, we next wanted to see how we can operate the motors provided, and see how we can power them efficiently. This was done using a few lines of coding and wiring both motors to a compact motor shield (L298n). The reason for the motor shield was to be able to dual run the two motor separately to allow for each one in turned to be turned off when needed.
void setup() ;pdp 2
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);
  pinMode(8, OUTPUT);
  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
  }
void loop() {
 digitalWrite(6,HIGH);
 digitalWrite(5,LOW);
 analogWrite(7,255);
 delay (100);
 digitalWrite(9,HIGH);
 digitalWrite(8,LOW);
 analogWrite(10,255);
 delay (100);

The next stage of this process was to code and wire up the new IR sensors, for this project we chose to use the tcrt5000 IR line tracking sensors. This was because; they are digital based so will be able to quickly differentiate between white space and the black line and they can be efficiently coded so that the motors will run as they are needed to. Here is the code we have used to allow these to work:
int a=11,b=12;
void setup() {
  pinMode(a,INPUT);
  pinMode(2,OUTPUT);
  pinMode(3,OUTPUT);
  pinMode(b,INPUT);
  pinMode(4,OUTPUT);
  pinMode(5,OUTPUT);
  Serial.begin(9600);
  }
  void loop() {
    if((digitalRead(a)==HIGH)&&(digitalRead(b)==HIGH))
    {       digitalWrite(2,HIGH);
digitalWrite(3,LOW);
      digitalWrite(4,LOW);
      digitalWrite(5,HIGH);
      Serial.println(“FORWARD”);
      delay(1);      }
      else if((digitalRead(a)==LOW)&&(digitalRead(b)==HIGH))
      {        digitalWrite(2,LOW);
        digitalWrite(3,HIGH);
        digitalWrite(4,LOW);
        digitalWrite(5,HIGH);
        Serial.println(“LEFT”);
        delay(1);         }
  else if((digitalRead(a)==HIGH)&&(digitalRead(b)==LOW))
        {          digitalWrite(2,HIGH);
          digitalWrite(3,LOW);
          digitalWrite(4,HIGH);
          digitalWrite(5,LOW);
          Serial.println(“RIGHT”);delay(1);        }  }

Using this code allowed us to record the data coming from the IR sensors. The serial monitor showed us that when both sensors were detecting white space, the motors would go forward. When the left is detecting black space then the car would turn left and vice-versa for the right-hand side.

pdp 3

Before moving on we wanted to see what sort of range the IR sensors had a how far from the ground we could place them. From this I could get up to 1.5cm working perfectly, and up to 2cm would still have enough accuracy.

The final stages of the electronics was to combine the two sets of codes and wire up the components up correctly. This is the result after running a series of tests:
int a=11,b=12;pdp 4
void setup() {
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);
  pinMode(8, OUTPUT);
  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);
  pinMode(a, INPUT);
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(b, INPUT);
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
  Serial.begin(9600); }

void loop() {  if((digitalRead(a)==HIGH)&&(digitalRead(b)==HIGH))  {
      digitalWrite(2,HIGH);
      digitalWrite(3,LOW);
      digitalWrite(4,LOW);
      digitalWrite(5,HIGH);
      Serial.println(“FORWARD”);
      delay(1);
      digitalWrite(6,HIGH);
      digitalWrite(5,LOW);
      analogWrite(7,200);
      delay (10);
      digitalWrite(9,HIGH);
      digitalWrite(8,LOW);
      analogWrite(10,200);
      delay (10);      }

      else if((digitalRead(a)==LOW)&&(digitalRead(b)==HIGH)) {
        digitalWrite(2,LOW);
        digitalWrite(3,HIGH);
        digitalWrite(4,LOW);
        digitalWrite(5,HIGH);
        Serial.println(“LEFT”);
        delay(1);
        digitalWrite(6,LOW);
        digitalWrite(5,LOW);
        analogWrite(7,50);
        digitalWrite(9,HIGH); //
        digitalWrite(8,LOW);
        analogWrite(10,100);
        delay (10);        }

        else if((digitalRead(a)==HIGH)&&(digitalRead(b)==LOW))  {
          digitalWrite(2,HIGH);
          digitalWrite(3,LOW);
          digitalWrite(4,HIGH);
          digitalWrite(5,LOW);
          Serial.println(“RIGHT”);delay(1);
          digitalWrite(6,HIGH);
          digitalWrite(5,LOW);
          analogWrite(7,100);
          digitalWrite(9,LOW);
          digitalWrite(8,LOW);
          analogWrite(10,50);
          delay (10);          }

          else if((digitalRead(a)==LOW)&&(digitalRead(b)==LOW))  {
            digitalWrite(2,HIGH);
            digitalWrite(3,LOW);
            digitalWrite(4,LOW);
            digitalWrite(5,HIGH);
            Serial.println(“STOP”);
            delay(1);
            digitalWrite(6,LOW);
            digitalWrite(5,LOW);
            analogWrite(7,0);
            delay (10);
            digitalWrite(9,LOW);
            digitalWrite(8,LOW);
            analogWrite(10,0);
            delay (10);            }

When testing the code, we had originally found that the response time for the sensors to the motors was too slow and was causing the car motors to hesitate before stopping. This would have caused problems when running the car as it may have caused the car to carry on going over the black line. This is why the delay times were dramatically reduced from 500 down to 10. This gave the motors a much quicker reaction time to what the data the sensors were sending. Also, a section was added to the code that stops the motors turning if the sensors detect no IR feedback. This means that the motors won’t run until placed down on a surface.

As you can see from the image above the wiring meant we could power the car straight from the Arduino. This can be done using a mini bread board to supply a universal power output and grounding to all the components.

The final stages of this as to build the body for the car. For this we wanted to have a nice aesthetic quality so we used a model car and vacuum formed a chases.

pdp 5

We then cut out a base for this and drilled holes along the base for all of the components to sit in:

pdp 10As you can see from the image above, we had originally put the IR sensors on top of the base. But after our initial tests we found that it was best to secure them underneath so that the sensors could be closer the surface; therefore, more accurate.
On the front you can see a 360-degree bovine style wheel, we used this so that all the driving force from the back of the car was not dampened or stopped by any bulky wheels.

pdp 7

The images above show different sets of wheels we tried out during the testing phase, and we found the large the wheel the better the car performed. Therefore, we did not use any gears of cogs as we believed the torque provided by the large wheels was enough for our car to complete a 10m track in under 5 minutes. We then decided than using thicker wheels would be best, and attached an elastic band to the double thickness wheels to provide more grip to a surface. Not using any extra gears also saved on weight, meaning the car would go faster anyway.

pdp 11

Finally, where will the egg go? Due to our simplistic design, we could leave enough space at the rear of the car for the egg to simply sit in underneath the chases.

Here is the final car:

pdp 8

As you can see from this image the egg comfortable sits at the rear of the car. This also provides a small amount of extra weight at the rear, which in this instance is good at providing extra traction to the wheels.

This project has been very beneficial as it has improved my coding abilities and given me the opportunity to work on all the problems that arose during the building stages of the car. The only thing left now is to run the car in the race at the end of this week and after testing the car, with a fresh battery, we believe it will be able to complete the course under the five minutes provided. I am very pleased with how the car has been finished: the aesthetic, the coding, the layout of the electronics and its capability to stay on the black line have all be worked through; giving us, what we believe, to be a great outcome for this project. If certain problems hadn’t caused us to lose time; the only improvements I would make would be to make it more compact, possibly use a smaller Arduino board and to add some small LED’s to the car to give a more professional finish. If we weren’t restricted by the brief to only use a single 9 Volt battery, we could also add extra power to the car to improve the driving force and therefore increase its speed and the duration at which it can run for.

Video to be added when assessment has been complete.

Providing Structure

More specifically, sharing the load. Now we know what a force is and how it acts on an object; we look to the real world and see that it much ore complex that that. What happens when more that one force is acting on an object?

If more the one element can share the load, amounts of material used in a product can be reduced. If we consider 2 cables hanging an object and they are equally distant and equally angled, then they will split the load between the 2 of them.
If the 2 cables are at different angles then the load will not be equal, but each load will vary depending on the different angles that the wire hang from.

Resolution of Forces (parallelogram of forces)

Remember that force is a vector quantity (size and direction) so we can draw a vector diagram!

  • Draw a line to scale that represents the force (e.g. 10N = 1cm)
  • Draw lines from the top of this at the same angle as the cables
  • Draw line parallel with angled lines, these lines intersect the angled lines completing the parallelogram

Disadvantage: if your drawing is not accurate then you will not get a correct result.

picture1

 

This example hear demonstrates 2 wires hanging at 30 and 60 degrees holding a 100N weight. The center line being 10cm long so each cm represent 10N, when measure the green line is 8.7cm and the Red line is 5cm long. It can therefore be assumed that the 30 degree cable is acting 87N of force and the 60 degree cable is acting 50N of force.

 

What happens If we are not given the T force, well that’s simple, it can be calculated using the following equation:

  • R= √(p2+q2+2pq coz θ)

R being the resulting force.
P and Q is amount of force acted on by the two cable (the above would be 87N and 50N).
θ is calculated from the sum of the 2 angled provided (the above would be 30deg and 60deg).

Columns and Struts

Columns are well tried and tested means of supporting loads particularly very heavy loads.
Stress = force/area
Failure modes is what happens when an object or material comes under so much force it starts to bend and warp this can be defined as Buckling this can be based on the angel and forces applied to a material.

Struts are a structural member which is subject to a compression force. Slender struts will fail by buckling before the yield point is reached. When the critical load is reached, the strut will buckle. The value of critical load depend on the end fixing conditions.

e.g. the struts in a car that keep is compression load correct.1pcs-lot-7514-soft-ruler-double-scale-infinite-bending-15-cm-students-ruler-free-shipping

Like a ruler, the longer the ruler the less force needs to be applied to start the buckling process. So, having a shorter ruler (of the same material) will make it stronger, or using thicker or other different shapes will increase its strengths to stop buckling.

 

If a strut buckles under the same load (W), the effective length (L) of each strut will be as shown below.

In a design, this idea can be used to figure out how long to make something before I buckles, either under its own weight, or the weight that it is holding. By using shorter and stronger materials the load can be spread more easily thus creating a stronger design.

Effective length = L x K
It is the length at which the materials buckles.

L = length of buckling
K = constant depending on how it is fixed (K is either 1, 0.5, 2 or 0.7)

picture2

A Bucking is a failure based on the angle at which it is compressed, depending on the force and how it is attached at either end.

Non-Axial Loads:

Columns do no always stand straight, the may fall at different angles.
Using a weight, you can give a column more stability.
Using a tie beam can reinforce a structure (archway) by taking the load via tension, so then it stops the angled force.
This means you can use thinner column and structures making it cheaper and much more efficient.

Picture3.png

Beams:
Two types of beams commonly used to build structures are called the cantilever and the simply supported beam.
Simply supported – fixed at both ends.
Cantilever – Fixed at one end.
Cantilever will droop because in undergoes a proportionate amount of strain at one end. When a weight is applied to the end the ore amount strain will be at the end where the beam is fixed.
Simply supported beams droop in the center only when a weight is applied to it. The most amount of strain will be either side of the beam where the beam is fixed.

Bending Moments:
If a load is place on the free end of a cantilever the beam droops because the bending moment increase the further you get away from the point of application of the load

  • Bending moment = force x distance
  • In our case L x W (length of beam x weight of object)

Upon Reflection:
I have learned that

  • Amounts of material can be reduced, by using more that one element to share the load.
  • I can provide stronger support from objects by using the correct fixing points.
  • A way to calculate the amount of force that can be taken from different cables hanging at different angles on different points on a object.
  • That weight and bar can be used to provide extra support for heavy roofed buildings
  • That there are 2 types of beams,  and how to provide strength to each type.

From this I aim to do more research into different materials I can use when supporting different weights and what kind of structures I would need to have when designing complex constructions.

Stressing and Straining

First off, a Tensometer. A device that used to measure the amount of stress or strain acting on an object in a given environment. It does so by applying a tensile load to a sample of material, and measuring the corresponding change in length. This can be plotted on a stress strain curve below:stressstraincurve

The elastic region is where a load can be placed onto a material but the material is still able to reform it original shape when the load is removed.

The plastic region is the point where the load on the material is too great so that it cannot reform to its original shape.

The point at which this happens is its Yield Point and the point at which the material will snap is known as the Failure Point.
The Yield Point can be calculated using Hooke’s law, that dictates that the extension of a material is proportional the force applied. Put simply Stress = E x Strain. Where E is a constant known as Young’s Modulus of Elasticity.  

Put in a practical situation: the higher the value of E the stronger the material

Example:
If we have a 3mm diameter steel wire supporting a mas of 50k?

  • What is the tension in the wire?
    Tension = mass x acceleration
    T = 50 * 9.81 = 490.5 N
  • What is the stress in the wire?
    Stress = Load/Area
    Area = pi r2 = 3.142 x 1.52x10-6 = 7.07×10-6
    Stress = 490.5 / 7.07×10-6
    = 69387466 (N/m2)
    Stress = 69.39 (MN/m2)
  • What level of strain would you expect?
    E = Stress/Strain
    Strain = Stress / E
    E can be found in a table of averages
    Stress we calculated in previous question
    Strain = 69.39 / 210,000
    = 0.33×10-3

So, if we assume that the wire is 1m then we say that the wire will stretch by 0.33mm when a 50kg weight is applied to it.

For design purposes this needs to be considered so that you can achieve a perfect product. For instance, how much weight you can put onto wire or cable before it can no longer hold that object. Also how much the wire or cable stretches may affect the overall shape of the design, therefore the design may need to change to suit the stretch of material.

Poisson Ratio
Something to consider on a tension and compression – when it is stretched the center will become thinner, the cross-sectional area with become smaller and vice versa with a compression.
This is known as Poisson Ratio
This can be calculated by = Transverse/longitudinal strain
Longitudinal strain = the change in length
Transverse strain = the change in the thickness of the area.

A practical use would be using cork in a wine bottle. Because its Poisson value is minimal, compared to rubber that has a higher value, so cork will not expand as much as rubber so will not get stuck in the bottle.
Materials will a lover value with not expand or compresses as much as a material with a higher value of poisson.

Shear stress and strain

The Same principles apply
Shear stress can be calculated by: Shear stress = F/A (Force/area)
and Shear strain = x/l (extension (amount is moved)/length)
Shear stress and strain will always act on the parallel axis.
For shear forces their constant is known as modulus of rigidity (G) and a materials table will be able to show you the modulus of both elasticity and rigidity and its poisson ratio.

sheer

This diagram shows you the effect of shear force on a parallel plane

 

 

The poisson value of each material can tell you how much it will move when a force is applied, as well as its tension and compression.

Strength of materials: These define what properties materials have and how they are either a strengthening property or a weakening.

  • Malleable meaning it can be deformed easily under compression without cracking
  • Ductile meaning it can be deformed easily under tension without fracturing. These can easily be drawn into wires
  • Tough since is can be bent to and fro before it will fracture.
  • Brittle materials can’t be bent to and fro without cracking or fracturing happening, small amounts of bending can be applied but only to an extent (e.g. glass)

 

Photo-elastic Stress Analysis
This is a simple and effective way of analyzing different stresses in product design and can be done like this:

  • Making a scale model of a product in a transparent plastic and placing the model in a beam or polarizing light.
  • Then apply a load to the model and observe the color (interference) patterns forming on the model.

These light patterns can determine the amount of stress or strain on a product. A polarised lenses will block light coming in from a certain angle, for instance in car mirrors to stop light from shining in your face.

fea

Different colors appear in different patterns when a force in applied to it. For instance, the colors will get brighter the more tension that is applied.
A polariscope is used to read the change in light patterns received, when a force in applied to the transparent plastic model. A special coating can be used to emphasize the light going through the model.

Advantages:

  • Can highlight possible failures due to unknown stressed by showing problems areas in a design. In practical use you can the areas in a design that need stronger materials.

Disadvantage:

  • Does not give you any numerical values to work with so the accuracy is limited.

 

Finite Element Analysis (FEA):

FEA consist of a computer model of a product that is stressed and analysed for specific results. They can test new products to see if it performs to the required specification prior to manufacture.

How it is done:

  • Create geometry 2D or 3D using a CAD package.
  • Create a meshing around he materials to analyse (looks like a grid). This contains all the structural properties to define how the structure will react to different load (force) conditions.
  • Assign a material, which will automatically assign values based on those material properties.
  • (They can also be used to read temperature analysis).

Structural Analysis: Simple linear models assume materials is not plastic-ally deformed. More complicated non-linear models consist of stressing the materials so that it can deform plastic-ally.

A similar test is Vibrational Analysis.
Simply put:

  • It is a type of analysis used to test a material against vibrations, shock, and impact.

Fatigue Analysis: Helps designers to predict the lift of a materials or structure by showing the effect of constant loading on the design. For instance, how long can a bell last when it is constantly being struck by something?

Heat transfer analysis:

Advantage –

  • Takes much less resources and time by jut altering the geometry on the computer software’s (ansys mechanical).
  • It is quick and accurate, being able to design and optimize it quickly.
  • Can predict a failure due to unknown stress loads being able to see hidden problem areas.
  • Allow designer to see all theoretical stresses.

Disadvantage –

  • If incorrect geometry or material in used then the calculations can be way off, causing problems I the future of the design

heat

This example of ‘ansys mechanical’ is showing stress on this object. The blue areas have no stress where the red areas have stress at the given example.

 

 

 

Upon Reflection:

What I have learned from this week is that all designs, no matter how big or small can be accurately tested to provide the best outcome for the structure of an object. This means that products can be made more durable and more efficient. When i go forward i my design practice I will consider these forces, especially when designing something that had a lot of weight. Doing so I will be able to calculate the exact materials to use that will provide maximum support and strength.

Don’t Break our Stool…

What a great start to our mechanical engineering project this term. First things first, mechanical engineering can be defined as the basis of how things work. This can be in all fields: chemical, biological and physical. the main focus is understand and study mechanisms.

Firstly the difference between something static and something dynamic. a static object has every force around it are acting in equilibrium so it remains stationary. Where a dynamic object has a force not acting at equilibrium so causes a movement or acceleration.

The resulting force of an object is the sum of all the forces acting on an object. This was quite intriguing to think as designer you would need to think about any forces that would act on a product to realise the best way to manufacture it.

We learned that the best way to define a force is that it is a push or pull caused by an interaction with an object. A great analogy (we were taught) for this is thinking of a door opening. When it is shut it is a static object, however when a push or pull (a force) is applied to it, it becomes dynamic, therefore it opens in the direction that the force was applied to.

door-opening

Direction being the key word in the previous statement, that because something can be defined by 2 categories, a Scalar or a Vector.

A scalar is something that has a quantity of magnitude (temperature or mass)

A vector has a quantity of magnitude, but also a direction. (Acceleration, force or velocity)

Force being a Vector, is measured in KgN, meaning Kilograms per Newton.

Moving onto to the late great Sir Isaac Newton.
issaac-newton

He was the first to define forces in a mathematical sense during the 1670’s.

We’ve all heard the story of the apple hitting him on the head and open reflections he realised that this falling force can be quantified and eventually calculated a 9.81m/s/s,

Using this we can calculate the weight of an object acting on the earth with the equation

W = mg, where m is the mass of the object and g is the gravity constant.

Isaac Newton created and lived by his 3 laws of Motion.

Laws 1 and 2 can be summed up by:

F = ma (mass x acceleration (rate of change of velocity)) where a = v/t (velocity/time)
A force occurs when a mass is accelerated.
Upon reflection of this it can be said when designing a car, it needs to have a light mass so that the acceleration can be higher.
If the force must be high to combat a heavy car, then there will be a high waste of energy that makes the car more expensive.

Law 3 can be simplified to this example: When throwing a ball at a wall then the wall will exert the same force back on the ball in the opposing direction so it will bounce back at the same rate it was thrown (Any reaction of force will always have an equal or opposite reaction or force).

These can be summarized with the diagram below:
3-laws

From all of this it can seen the Weight is a force so the two equations W = mg is the same as F = ma where a as acceleration is a variable that can be changed, instead of g for gravity that is a constant.

Moving on from this, all forces acting on the structures around them.

There are 4 primary ways that forces can be transmitted within a structure.

Tension – like a wire hanging something from a ceiling (to prevent on object acceleration the string holing it mustard pull in the opposite direction with an equal and opposite force.) What is the tension strength it can reach before it snaps apart?

Compression – forcing two objects together. (a brick on a column, because the column cannot move it pushes back with an equal and opposite force to the weight of the brick.) What is the compression strength of dick it can reach before is breaks?

Torsion – the rotation of an object. Attaching a steel bar to a wall, then using a grip at the other end, will rotate the bar making it look like a corkscrew. How much can you rotate an object before it snaps?

Shear – objects sliding against each other (when looking at glue, you see the shear strength of how much force it can take before it breaks.) e.g. a pin or rivet is subjected to a shear across a plan surface or axis.4-ways-of-force

These can all be seen in the diagram here:

 

 

 

 

From this we started looking at materials:
They will always behave differently depending on force and temperature and other factors
E.g. a steel rood is good a resisting a tensile force, where concrete is very good at resisting compression force.

More terms…

Stress – When a force is acting on object that causes a stress (Stress = force applied/area it is applied to). If we can calcite the maximum stress of a component we can work out if it will be strong enough. How much area would need to hold a force of so much before the stress is too much. For instance, how much material is needed to carry a load and what’s the maximum load that material can take. Cross sectional area, in a cylinder that can be calculated by (piR2).

Example – crane wire – mass of 1 tonnes suspended from a wire rope from the crane. How thick does the wire rope have to be if it had a cross sectional area of 100mm2?

So, 1000 x 9,81 (N)/100×10-6 (m2)

=98.1 MN/ m2 (MN = Mega Newtons stands for 10x6)

(10-6 changes the units to meters, because there are 1,000,000 mm2 in 1m2)

How do we know if it will be strong enough? Strain can tell us!

Strain – change in length/original length. Stress can be both tensile and compression. So we know materials react to stress creating a strain by distorting or changing shape.
How much does a material change shape for a given stress level? Depends on…
type of material
shape of the component
type of stress that is applied to it (tension, compression)
A thermos is round because the shape is very good at taking the forces from the vacuum created inside the product.
This information is critical for a product designer to realise how to make a new product for it to look good, as well as work well and is strong enough for purpose.
Strain = change in length/original length (ΔL/L)

In Summary:

Force = Mass * Acceleration
Newtons laws
Stress = Load/Area
Strain = change in length/original length.

Finally to the title of this blog!! – Don’t break our Stool…

This was in reference to the practical assignment we were set in the last hour of our class. We were given a large sheet of card and asked to make a 25cm tall stool, that could support the weight of a our lecturer. This as to be done in groups of 3.

We were given tape to keep the card together and the information that the lecturer as approximately 80 Kg in mass. At first we thought about calculating the weight that the lecture would put onto the stool and the amount of strain he the material would need to take to support this. Quickly we realised that this was not getting us anywhere and deiced that the cylinder was the perfect shape for the stool due to its strong shape and large surface area it could create. Here was our product, that was able to support the lecturer.

As you can see we gathered together lots of cylinders and compressed them together using a large cover. The cover also doubled as the stand for the lecturer. This would offer maximum spread of weight over all of the strongly shaped cylinders below.

Quick Summary:

I have thoroughly enjoyed this mornings session and look forward to progressing with project. I have learned that all kinds of things have to be considered with the mechanics of a design. Including the way a person uses a design and the forces implemented, that may cause strain to it structure. 

Final Game (RED light GREEN light)

int ledList[2] = {0,1}; //declaring array for LED’s
int ledPins[2] = {11,12}; //declaring pins for LED
int pirPin = 10; //declaring sensor
int buttonpin = 9; //declaring pin for button
int buttonstate = 0; //declaring button state
boolean pirState = 0; //declaring pir state for change
long timer = 0;
long lastTimer = 0;
long interval = 2000;

void setup() {

pinMode(ledPins[0], OUTPUT); //setting LEDs both off
pinMode(ledPins[1], OUTPUT);
Serial.begin(9600);
Serial.print(“Calibrating”);
delay(40000);
Serial.print(“Calibration complete”); //initialising game
pinMode(pirPin, INPUT); //setting input pins for pir sensor
Serial.begin(9600);
delay(1000); //allowing 5 seconds for pir sensor to ouput

}

void loop() {
//pirState = digitalRead(pirPin);
//Serial.println(pirState); //setting pirpin to output the pir state

//digitalWrite(ledPins[0], LOW); //turning LED’s off
//digitalWrite(ledPins[1], LOW);

timer = millis();

if(timer – lastTimer >= interval) {
int randNumber = random(2); //selected randon LED
Serial.println(randNumber); //output randon LED
if (randNumber == 0){
ledList[0] = 1;
ledList[1] = 0;
}
else {
ledList[0] = 0;
ledList[1] = 1;
}
lastTimer = timer;
if(ledList[0] == 0){ // Green On
digitalWrite(ledPins[1], HIGH);
digitalWrite(ledPins[0], LOW); //Tunrs Red LED on
Serial.println(“Stop Moving!”); //outputs message

}
else { // Red On
digitalWrite(ledPins[1], LOW);
digitalWrite(ledPins[0], HIGH); //Tunrs Green LED on
Serial.println(“You Can Move!”); //Outputs messege
//delay (1000); //delays output to give people time
pirState = digitalRead(pirPin);
Serial.println(pirState); //outputs pir sensor reading
}
//delay(2000);
}

pirState = digitalRead(pirPin);
if (ledList[1] == 1 && pirState == 1) {
Serial.println (“GAME OVER, YOU LOSE”);
}

buttonstate = digitalRead(buttonpin); //sets an output for the button state

if(buttonstate == HIGH) { // 2 equals signs means a test where 1 menas its true
Serial.println(“GAME OVER!!, You are the winner”); //outputs a winning messege when the button is pressed
}

}

Here is our final code, allowing the game to work. It simply shows the green LED and lets people move. Then the red LED shows and tells people to stop moving. The PIR sensor then kicks in and if it notices movement the game then outputs a message telling the players they have failed. The winner is the person who can get to button at the end whilst the green light is on and haven’t been caught by the PIR sensor when red LED is on.

15398955_1582151381802457_1759428834_o

Above is the wiring set onto the bread board and arduino, with the 2 LED’s in pins 11 and 12, the button in pin 9 and the PIR sensor in pin 10.

I have definitely enjoyed this project and i look forward to finishing this game and to make it run much smoother. What i mean by this is we could add a gaming case and add to the code so that we could change the difficulty or add a distance measurement to indicate individuals who moved during the red LED phase.

I am anxious to see what this new knowledge of arduino software will help me with in my future projects. The hardest part about this was figuring out how to turn a sudo code into the real code, and understanding what parts of the coding language could be used to make the game much more efficient. Over Christmas I aim to work on my coding language knowledge and I shall attempt to find a more efficient way to run my codes in the future. For instance in the code above you can see the use of a delay function, this could be helped by replacing it with a “millis” function to keep track of the timing in the code. This I did with one of the delay functions I used. I was however; given the time i had left, unable to put this function into the other delay that is there.

Again i look forward to carrying this on next time, but for now I shall work on this over the Christmas break and see what else I can learn to take back next term.